Stable output control of a liquid rocket engine is one of the main methods that countries who have advanced rocket technologies use in order to launch a payload of a rocket into a target orbit. In particular, a projectile which uses a liquid propellant reduces the thrust of a propulsion engine in order to maintain the thrust depending on a designed mission flight or to ensure a safe stage separation. For this purpose, active control is carried out using a control valve instead of a fixed orifice in order to maintain and fix the flow rate of the propellant to be constant depending on a preset value of thrust.
A typical industrial control valve which is used for such active control is configured such that it uses a pneumatic actuator which requires a large amount of force and its weight is increased by periphery devices which are used for control, which is problematic when the valve is applied to a liquid rocket engine for aviation.
In the meantime, as demand for satellites is rapidly increasing due to various communication needs or the like, countries having advanced technologies in aerospace fields, such as the USA, Russia, European countries and Japan, are acquiring liquid rocket technologies with which a large satellite can be launched into an intended orbit. The acquirement of the technology for precisely controlling a complicated propulsion system, i.e. properly controlling the mass of a propellant and a thrust depending on the orbit of a liquid rocket, is indispensable for the development of liquid rockets.
In such a liquid rocket, thrust reduction is carried out for the purpose of separation between stages and protection of a payload. During the thrust reduction, the thrust is uniformly adjusted to prevent any problems from occurring in the liquid rocket. In the case of a liquid rocket, this object can be realized by controlling the flow rate of a liquid that is consumed in order to adjust the thrust. Consequently, countries having advanced technologies for projectiles control a flow rate valve of a liquid rocket using an algorithm that they have developed themselves. However, no such technologies are known in the Republic of Korea.
Accordingly, the present invention is intended to propose a multistage control method of a flow rate control valve using a DC motor which can precisely control a flow rate by rotating the DC motor at an intended angular speed.